1. Technical Field of the Invention
The present invention relates to polymer coatings or varnishes able to confer, in particular, anti-fouling properties to supports, especially:
flexible support substrates, in particular fibrous, woven or nonwoven supports, that may or may not be coated with at least one mechanical reinforcement or protective layer, based on a coating polymer of the silicone elastomer type, for example;
bulk supports made of silicone and/or coated with one or more layers of silicone, for example metal, plastic or ceramic parts (e.g., electrical insulators);
or else polymeric or elastomeric supports, in particular plastic films, for instance: thermal transfer ribbons for use in particular as an ink support in heat transfer printers; or protective packaging films.
These supports may optionally at least partly be made of silicone.
The present invention also relates to methods for applying the anti-fouling varnish, to which it relates, onto various supports.
Too, this invention also relates to supports coated with such anti-fouling varnishes, and in particular flexible supports such as textile cloths coated with a layer of silicone elastomer to which the anti-fouling varnish is applied, such cloths being useful for producing:
1. architectural textiles (elements of textile architecture);
2. or else flexible supports other than architectural textiles.
As regards the field of application 1, it should be appreciated that, throughout the present disclosure and for the purposes of the present invention, the term “architectural textile” means a woven or nonwoven fabric, and more generally any fibrous support useful, after coating, for making up:
shelters, movable structures, textile buildings, partitions, flexible doors, tarpaulins, tents, stands or marquees;
furniture, claddings, billboards, windshields or filter panels;
solar protection panels, ceilings and blinds.
As regards the field of application 2, it will be appreciated that these flexible supports other than architectural textiles may, for example, be those intended for the production in particular of:
airbags used for protecting the occupants of a vehicle,
glass braids (woven glass sheets for thermal and dielectric protection for electrical wires),
conveyor belts, fire-barrier or thermal insulation fabrics,
clothing,
compensators (flexible sealing sleeves for pipe work), etc.
Because of the intrinsic properties of silicones, the silicone elastomer coatings on textile supports already provide the composites thus formed with many advantages, namely, inter alia:
flexibility,
mechanical strength,
heat resistance,
and longevity.
However, in the field of textile architecture, which constitutes an important application for the abovementioned composites, other requirements have been formulated, which are in particular the following:
resistance to fouling,
ability to bond so as to allow ready assembly of the composites two by two (for example, with an adhesive force F≧70 N/5 cm, and preferably F≧120 N/5 cm),
low slip coefficient so as to promote handling of the composite, for example equivalent to a Kd≦0.8,
good characteristics of appearance, in particular with regard to color and gloss,
good cohesion of the composite.
These properties can be provided by a varnish. The general problem forming the basis of the invention is therefore the development of a silicone varnish able to fully accomplish this role, in particular with regard to anti-fouling qualities.
However, before satisfying the requirements relating to the final applications intended for the composite, it is important for this varnish to satisfy, moreover, upstream specifications, namely, in particular:
to be able to be readily spread over a silicone layer,
to adhere completely to this silicone layer,
and more generally, to be easy and economical to use in industrial terms.
2. Description of Background and/or Related and/or Prior Art
WO-A-00/59992 describes silicone compositions that are especially useful for producing varnishes which can be applied to supports whose friction coefficient it is desired to decrease.
One of these compositions comprises:
at least one polyorganosiloxane (POS) A that is crosslinkable by means of crosslinking functional groups (CFGs) via the cationic and/or radical pathway:

an initiator C selected from onium borates:
C=

and at least one silylated compound D substituted with secondary functional groups (SFGs), preferably of alkoxy type, carried by silicon atoms and selected from those comprising at least one alkoxy and/or epoxy and/or carboxyl unit, and optionally CFGs of (meth)acrylate and/or vinyl ether and/or epoxide and/or oxetane, preferably epoxide, type; they may, for example, be the following compounds:                silane of type:        
                POS of type:        

and, optionally, a filler (e.g., silica), for example: pyrogenic silicas treated with hexamethyldisilazane or with octamethylcyclotetrasiloxane (specific surface area up to approximately 300 m2/g), fumed silicas, ground synthetic or natural fibers (polymers), calcium carbonates, talc, clays, titanium dioxides, etc.
Such compositions are used as anti-fouling varnishes for RTV silicone coatings of fabrics for airbags, for thermal transfer ribbons or for packaging films.
Such varnishes can be improved in terms of anti-fouling properties, of bonding ability, or even of reduction in slip coefficient. In addition, they require the use of specific silicones that are crosslinkable via the cationic pathway with UV activation, which leaves a margin for improvement in economic terms and in terms of simplification of the means implemented.
It therefore appears that the prior art is essentially devoid of anti-fouling varnishes compatible with silicone elastomer coatings for supports, in particular textile supports, and even less so in anti-fouling varnishes that satisfy the above specifications.